Both military and civilian agencies are increasingly being required to provide or restore public order or to act in peace keeping or security roles. Further many modern warfighters are being required to operate in urban environments with large resident civilian populations, whilst being on guard for possible attack by enemy combatants who may be largely indistinguishable from the local population.
To assist such agencies in providing such roles, various non lethal weapons systems and projectiles have been developed. Such systems allow the user to modify an aggressor's intent by striking them at range with a “controlled or measured” amount of kinetic energy, which is delivered to the body by the impact of a “Non Lethal” projectile. Other types of non lethal rounds include those which deliver electrical charges to the target (eg TASER™) or non lethal projectiles such as stunning (eg sound), smoke, or irritant (eg capsicum or tear gas) rounds. Generally the non lethal munitions used in 40 mm, 37 mm or 12 gauge weapons are designed to be used only within a prescribed or fixed zone of employment. In other words the weapon can only be fired safely within a certain range or distance band.
This fixed “zone of employment” results from the fact that current non lethal munitions are fired with fixed launch velocity and hence manufactures optimise their ammunition to meet a specific set of design requirements unique to that zone. For example, the M1006 point impact non lethal round used by US and Australian defence forces is designed to be fired between a minimum range and a maximum range out to 50 m. The fixed launch velocity of the round limits its use to this zone and hence the round is considered to be unsafe to employ under 10 m, and ineffective beyond 50 m. In reality, the sweet spot at which the round is safe and effective is smaller than this “optimum” zone. Such problems are typical of such systems.
The difficulty faced by the military user of non lethal weapons systems is that modern complex asymmetric type operations dictate that the scenarios are wide and varied and hence these weapon systems should be as flexible as possible to meet the changing engagement circumstances. Current approaches have consequently led to the undesirable requirement to carry multiple ammunition types (each with their own zone of employment which may or may not overlap) or to limit the employment options to a tight set of conditions which severely restricts the user's options in the field. Logistically this burdens the operation by requiring the organisation to carry and support a range of munitions options.
Some attempts have been made in the past to construct variable velocity munitions for other applications. These have typically used multiple propellant charges which are selectively ignited, however these suffer from a range of deficiencies making them unsuitable for use in the non lethal setting. For example some systems include propellant in the projectile. When the projectile is not fired to the maximum range (common in non lethal settings), not all of the propellant is consumed, leaving the projectile in an unsafe state which is undesirable in a non lethal scenario. Another system includes selectable charges located in the cartridge. However this creates safety issues for the user of the system, as when the projectile is not fired to the maximum range the ejected casing will still contain unconsumed propellant.
There is thus a need to provide a non lethal weapons system that is suitable for safe and effective use over a wider employment zone than current systems, or at least to provide users of existing systems with a useful alternative.